Start Trek II: Wrath of Khan
John Carpenter's The Thing
I would put the Empire Strikes Back, but I consider that to be science fantasy, as opposed to science fiction.
Blade Runner is another of my favorites, just not as high, but really --watchable anytime.
I like most of the Star Trek movies, some more than others, but don't have them in my list, except for the reboot. I really like Star Trek as a go to anytime, any of the movies.